Amblyopia - Causes and How it can be treated

The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain.

Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly.

The eye itself looks normal, but is not being used normally because the brain is favouring the other eye. It is a gross difference of vision in the two eyes. This condition is also sometimes called lazy eye.

Amblyopia is a common cause of visual impairment in childhood. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children and young and middle-aged adults.

What causes amblyopia?

Amblyopia may be caused by any condition that affects normal visual development or use of the eyes. Amblyopia can be caused by strabismus, an imbalance in the positioning of the two eyes.

Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Sometimes amblyopia is caused when one eye is more nearsighted, farsighted, or astigmatic than the other eye.

How is amblyopia treated in children?

The treatment of amblyopia is most effective when done early in the child's life, usually before age 7; after this there is no treatment. Treating amblyopia involves making the child use the eye with the reduced vision (weaker eye). There are two ways used to do this:

Patching

The classic and best treatment for Amblyopia is to put a full time opaque patch on the normal better seeing eye. This therapy forces the child to use the eye with amblyopia. Patching stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.

The patch is worn full-time during waking hours except for 1 hour per day. The child is patched 1 week per year of life. If a child is 7 years of age, therefore this means he gets a full-time patch for 7 weeks.

Three cycles of full-time patching should be tried. Patching can be achieved by several different means and the doctor can tell the best way. Patching forces the amblyopic eye to see and this develops the vision in that eye.

Atropine

A drop of a drug called atropine is placed in the stronger eye once a day to temporarily blur the vision so that the child will prefer to use the eye with amblyopia.

Can amblyopia be treated in adults?

During the first six to nine years of life, the visual system develops very rapidly. Complicated connections between the eye and the brain are created. Scientists are exploring whether treatment for amblyopia in older children and adults can improve vision, but there are no standard guidelines yet.